The survivors make some disarming discoveries not only about the aliens but also about themselves. Mokrani goes on the offensive, taking the fight to the aliens. Ash is forced to make the hardest decision of his life. And Chloe's past catches up with her, threatening to rip apart the delicate semblance of normality she is so desperately clinging on to.

The alien's connection to certain survivors raises difficult questions. Bill makes a startling discovery. Sacha's behaviour is increasingly erratic. And Tom's birthday proves cause for celebration. But at what cost?